build script: Fix message on failed download (fixes #456) (#457)

Message displayed when file download fails, shows wrong information
about maximum number of attempts. Hardcoded value of '3' is shown,
but in reality there is up to six attempts (when subsequent downloads
keep failing).
Fix it by using correct value.

build-package.sh

@@ -161,7 +161,8 @@ termux_download() {
 
 	TMPFILE=`mktemp $TERMUX_PKG_TMPDIR/download.$TERMUX_PKG_NAME.XXXXXXXXX`
 	echo "Downloading ${URL}"
-	for i in 1 2 3 4 5 6; do
+	TRYMAX=6
+	for try in $(seq 1 $TRYMAX); do
 		if curl -L --fail --retry 2 -o "$TMPFILE" "$URL"; then
 			if [ $# = 3 ]; then
 				# Optional checksum argument:
@@ -173,7 +174,7 @@ termux_download() {
 			mv "$TMPFILE" "$DESTINATION"
 			return
 		else
-			echo "Download of $1 failed (attempt $i/3)" 1>&2
+			echo "Download of $1 failed (attempt $try/$TRYMAX)" 1>&2
 			sleep 45
 		fi
 	done